A wind power generator is conventionally known that uses wind power as natural energy to generate power. The wind power generator includes a rotor head having a wind turbine rotary blade (hereinafter referred to as “wind turbine blade”) mounted to a nacelle provided on a column, a main shaft coupled to the rotor head to rotate with the rotor, a speed-increasing gear coupled to the main shaft rotated by wind power applied to the wind turbine blade, and a generator driven by shaft output power of the speed-increasing gear, and the parts are appropriately supported by a bearing. In the wind power generator having such a configuration, the rotor head including the wind turbine blade, which converts wind power into torque, and the main shaft are rotated to generate the shaft output power, and shaft output power with an increased number of rotations is transferred to the generator via the speed-increasing gear coupled to the main shaft. Thus, the shaft output power obtained by converting wind power into torque is used as a drive source of the generator, thereby allowing power generation using wind power as power of the generator.
In the above described wind power generator, particularly, a wind turbine blade has become longer than conventional ones because of a recent increase in size of the wind power generator. Such a wind turbine blade having an increased length is recently devised to be colored such that the wind turbine blade is coated with an ultraviolet reflection coating to prevent birds from accidentally colliding with a rotating wind turbine blade (for example, see PTL 1), or that the wind turbine blade is colored blue as a daytime sky color or with a greenish color to be harmonized with a background of a wind power generation facility and look smaller (for example, PTL 2 and PTL 3).
Since rain or dust in air repeatedly collides with the wind turbine blade, a surface of the wind turbine blade is deformed and deteriorated, and a material is gradually eliminated. This may cause erosion that is wear reducing a thickness. In particular, for an off-shore wind power generator provided on the ocean, a wind turbine blade may be affected by salt corrosion. Thus, conventionally, in regular inspections of the wind power generator, an operator visually checks a degree of wear during a stop of rotation of the wind turbine blade, and performs maintenance when there is serious wear.